1. Field of the Invention
This invention relates to a molding process for manufacturing a molded article, more particularly to a molding process for manufacturing a molded article formed with a channel.
2. Description of the Related Art
Molded articles for decoration, souvenir, stationery and the like are normally provided with channels for various purposes. FIG. 1 illustrates a letter opener 1 including a blade 11 and a handle 2 with a channel 10 for insertion of the blade 11. FIGS. 2 to 4 illustrate how a channel 132 is formed in a molded decoration 14 made of a metal. The decoration 14 is prepared by molding the metal in a mold 12 which includes upper and lower mold halves 120, 121 confining a mold cavity therebetween. Two pairs of opposite positioning grooves 122 are respectively formed in confronting surfaces of the upper and lower mold halves 120, 121 at two opposite sides of the mold cavity, and are communicates with the mold cavity. To form the channel 132 in the decoration 14, a rigid hollow rod 13 is placed in the mold cavity with two opposite ends being placed and positioned in the grooves 122. Metal in a melted state is then introduced into the mold cavity and is molded over the rod 13 to form a molded part. The two opposite ends of the rod 13 that protrude outwardly from the thus formed molded part are subsequently cut off (see FIG. 3) or the rod 13 is completely withdrawn from the thus formed molded part to form the channel 132 in the decoration 14 (see FIG. 4). When the rod 13 is to be withdrawn from the molded part in the process of forming the channel 132, the rod 13 can be solid instead of being hollow.
The manufacture of the decoration 14 is disadvantageous in that since a portion of the rod 13 remains in the decoration 14 and since the protruding portions of the rod 13 are cut off and will become waste, the manufacturing cost will be increased and disposal of the waste will be troublesome. Moreover, since the rod 13 is tightly surrounded by the molded part, it is difficult to withdraw the same from the molded part. There is thus a tendency for the molded part and/or the rod 13 to be damaged during the withdrawing action.
The mold 12 described above can only produce a channel having a simple shape, and requires the grooves 122 to be formed in the confronting surfaces of the upper and lower mold halves 120, 121. When a channel (indicated as reference number 133xe2x80x2 in FIG. 6) having a complex shape, such as a curved shape or a bent shape, is to be formed in a molded part 14xe2x80x2, or when a plurality of channels 132, 132xe2x80x2, 133, 133xe2x80x2 extending in different directions are to be formed in molded parts 14xe2x80x2, 14xe2x80x3 (see FIGS. 5 and 6), a multi-piece mold (i.e. more than two pieces) is required for manufacturing the molded part. As such, the manufacture of the molded part becomes very complex and costly. While the channel 132, 133 in the molded part 14xe2x80x2 can be formed by drilling, the drilling process is time consuming and can result in an enormous increase in production cost. Furthermore, it is impossible to form the channel 133xe2x80x2 of the mold part 14xe2x80x3 by drilling. In an alternative method, the channels 132, 132xe2x80x2, 133, 133xe2x80x3 in the molded parts 14xe2x80x2, 14xe2x80x3 are formed by separating the molded parts into different pieces. At least two mold pieces are needed to combine with each other by welding or gluing to form each of channels 132, 132xe2x80x2 133, 133xe2x80x2. However, the welding process or the gluing process is also time consuming, and there is a tendency for the mold parts 14xe2x80x2, 14xe2x80x3 to break at locations where the welding or the gluing is applied. Moreover, when two channels in two pieces are connected to form a channel in the assembled piece, and when the channel is to be used for storing liquid, there is a tendency for the liquid to leak at locations where the welding or the gluing is applied.
Therefore, the object of the present invention is to provide a molding process for manufacturing a molded article that is capable of overcoming the aforementioned drawbacks.
According to the present invention, a molding process for manufacturing a molded article comprises the steps of: (a) preparing a mold having a mold cavity that has a shape conforming to that of the molded article, and a positioning groove disposed externally of and in communication with the mold cavity; (b) preparing a flexible tube; (c) placing the tube in the mold cavity and positioning one end of the tube in the positioning groove; (d) closing the mold and introducing a molding raw material into the mold cavity around the tube to form a molded part that encloses a portion of the tube; (e) removing the molded part together with the tube from the mold cavity; and (f) withdrawing the tube from the molded part to form a channel in the molded part.